Dihydroxyglyoxime and its recrystallization method, additive

Abstract

The application discloses a kind of dihydroxy glycol oxime and its recrystallization method, additive.The method comprises the following steps: firstly, dry dihydroxy glycol oxime crude product is dissolved in distilled water, and the first mother liquor of specified concentration is prepared at a specific temperature, and the second mother liquor is collected after the initial product is filtered and room temperature is placed;Then, with the second mother liquor as solvent, add a new batch of dihydroxy glycol oxime crude product, heat to set temperature to form the third mother liquor of specified concentration, and the product is obtained again after filtering after the temperature of room temperature standing or stirring program cooling crystallization and the fourth mother liquor is obtained;The above-mentioned mother liquor recycling step is repeated, and the efficient reuse of solvent is realized.The method optimizes the recrystallization process parameters, realizes the multiple recycling of mother liquor under the premise of ensuring the purity of product, significantly improves the recrystallization yield of dihydroxy glycol oxime, and has obvious economic benefits and environmental friendly characteristics.

Description

Technical Field

[0001] This application relates to the field of preparation of dihydroxyethylenedioxime, and more particularly to a dihydroxyethylenedioxime, a recrystallization method thereof, and an additive. Background Technology

[0002] Dihydroxylglyoxime (DHG) is an energetic material with excellent thermochemical properties. It has a low enthalpy of formation (-570.28 kJ / mol), and its decomposition products are mainly fuel-rich gases (such as CO, CO2, H2O, and N2), making it environmentally friendly, safe, and with controllable energy release. It can be used as an oxidant to replace ammonium perchlorate (AP) or ammonium nitrate (NH4NO3) to reduce propellant combustion temperature and control combustion rate, while reducing the high corrosiveness and environmental risks of traditional oxidants. Liquid DHG can be added as a combustion improver to fuels such as mosquito coils, honeycomb briquettes, and coal briquettes to improve combustion efficiency and lower combustion temperature. Its low combustion temperature can also be used as a gas source and diffuser to promote the uniform distribution of active ingredients in pesticides. Due to the versatility of DHG, the demand for its industrial production continues to grow, but the economic and environmental aspects of existing preparation processes urgently need optimization.

[0003] Currently, the industrial production of DHG mainly relies on crystallization purification technology to achieve the separation of high-purity products. A typical process flow is as follows: 1. Synthesis reaction: Diethyl oxalate, hydroxylamine hydrochloride, and sodium hydroxide are reacted in an ethanol-water mixed solvent to produce crude DHG; 2. Recrystallization purification: The crude product is dissolved in a solvent (such as water or an ethanol-water mixture), and crystals are induced to precipitate by controlling parameters such as temperature and stirring rate. The purified product is finally obtained through filtration. However, the single-step yield of the recrystallization step is usually less than 70%, resulting in low raw material utilization; the mother liquor generated after crystallization (containing unprecipitated DHG and some impurities) is not effectively recovered, and direct discharge increases wastewater treatment costs; some crystal particle sizes do not meet the requirements of subsequent applications, but existing technologies do not provide effective recovery or reuse methods.

[0004] Therefore, there is an urgent need to provide a method to improve the recrystallization yield of dihydroxyethylenedioxime and obtain dihydroxyethylenedioxime with the target particle size and high particle size uniformity. Summary of the Invention

[0005] This application provides a high-yield dihydroxydioxime, its recrystallization method, and additives to improve the crystallization yield and particle size uniformity of dihydroxydioxime.

[0006] In a first aspect, embodiments of this application provide a method for recrystallizing dihydroxyethyl oxime, comprising:

[0007] Step 1: Dissolve the crude dihydroxyethyl oxime in deionized water to obtain the first mother liquor;

[0008] Step 2: Let the first mother liquor stand and perform a first separation, collect the filtrate, add a co-solvent to the filtrate, and perform a second separation to obtain a second mother liquor and a first precipitate;

[0009] Step 3: Add crude dihydroxyethyl oxime to the second mother liquor to obtain the third mother liquor;

[0010] Step 4: Crystallize the third mother liquor to obtain the fourth mother liquor and the second precipitate;

[0011] Step 5: Repeat steps 3 and 4 to wash and dry the first precipitate, the second precipitate, and other precipitates to obtain the dihydroxyethylenedioxime;

[0012] The co-solvent includes at least one of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate.

[0013] In one possible implementation, dissolving the first crude dihydroxyethyl oxime in deionized water comprises:

[0014] The crude dihydroxyethyl oxime was dissolved in deionized water at a first dissolution temperature of 45℃-85℃ and stirred for 5min-45min to obtain the first mother liquor.

[0015] And / or, the step of allowing the first mother liquor to stand and performing a first separation includes:

[0016] After the first mother liquor is left to stand at a temperature of less than or equal to 30°C for 48-96 hours, the first separation is performed, and the filtrate is collected.

[0017] And / or, the addition of the second crude dihydroxyethyl oxime to the second mother liquor comprises:

[0018] The second crude dihydroxyethyl oxime was dissolved in the second mother liquor at a second dissolution temperature of 45℃-85℃, and stirred for 5min-45min to obtain the third mother liquor;

[0019] And / or, the crystallization treatment of the third mother liquor includes:

[0020] The third mother liquor is cooled at a stirring rate of 200 rpm to 400 rpm and a cooling rate of 0.1 °C / min to 1 °C / min. Then, it is allowed to stand at a temperature of less than or equal to 30 °C for 48 h to 96 h for crystallization treatment and filtration to obtain the fourth mother liquor and the second precipitate.

[0021] In one possible implementation, the first mother liquor contains dihydroxyethylenedioxime;

[0022] The mass fraction of dihydroxyethyl oxime in the first mother liquor is 0.61wt%-1.80wt%.

[0023] In one possible implementation, the mass fraction of the dihydroxyethyl oxime in the first mother liquor is 1.48wt%-1.80wt%.

[0024] In one possible implementation, the mass concentration of the co-solvent in the second mother liquor is 0.5 mg / mL to 2.0 mg / mL.

[0025] In one possible implementation, the third mother liquor comprises dihydroxyethylenedioxime;

[0026] The mass fraction of dihydroxyethylenedioxime in the third mother liquor is 0.53wt%-1.57wt%.

[0027] In one possible implementation, the mass fraction of the dihydroxyethyl oxime in the third mother liquor is 1.16 wt% to 1.80 wt%.

[0028] In one possible implementation, the cooling rate during the crystallization process is 0.2°C / min to 0.5°C / min.

[0029] And / or, the settling temperature is less than or equal to 20°C;

[0030] And / or, the settling time is 60h-84h.

[0031] In one possible implementation, the number of repetitions in step four is greater than or equal to 3.

[0032] Secondly, embodiments of this application provide a dihydroxyethyl oxime, obtained by the above-described recrystallization method.

[0033] In one possible implementation, the particle size of the dihydroxyethylenedioxime is 800 μm-2500 μm;

[0034] The standard deviation of the particle size of the dihydroxyethyl oxime is less than or equal to 60 μm.

[0035] Thirdly, embodiments of this application provide an additive comprising the above-mentioned dihydroxyethylenedioxime.

[0036] This application provides a method and additive for recrystallizing dihydroxyethylenedioxime and its recrystallization. By using mother liquor recycling and adding a co-solvent during the recycling process, the crystal growth and nucleation rates are balanced, the generation of excessively fine particles is reduced, the particle size uniformity is improved, and efficient recrystallization of dihydroxyethylenedioxime (DHG) is achieved. At the same time, the problems of mother liquor waste and waste of products with non-target particle size are solved, forming a closed-loop resource utilization system. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0038] Figure 1 A schematic diagram of the crystal morphology of dihydroxyethyldioxime provided in this application;

[0039] Figure 2 PXRD patterns of dihydroxyethylenedioxime and standard dihydroxyethylenedioxime samples provided in this application;

[0040] Figure 3 This is a schematic diagram of the particle size and particle size distribution data of dihydroxyethyl oxime provided in this application.

[0041] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0042] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0043] First, let me explain the terms used in this application:

[0044] In the existing technology, dihydroxyethyl oxime obtained by recrystallization has technical problems of low yield and waste of resources.

[0045] The recrystallization method provided in this application solves the technical problems of resource waste and uneven particle size of dihydroxyethyl oxime by means of mother liquor recycling and the use of co-solvents.

[0046] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0047] This application provides a method for recrystallizing dihydroxyethyl oxime, the method comprising:

[0048] Step 1: Dissolve the crude dihydroxyethyl oxime in deionized water to obtain the first mother liquor;

[0049] Step 2: Let the first mother liquor stand and perform the first separation, collect the filtrate, add a co-solvent to the filtrate, and perform the second separation to obtain the second mother liquor and the first precipitate; the co-solvent includes at least one of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate;

[0050] Step 3: Add the second crude dihydroxyethyl oxime to the second mother liquor to obtain the third mother liquor;

[0051] Step 4: Crystallize the third mother liquor to obtain the fourth mother liquor and the second precipitate;

[0052] Step 5: Repeat steps 3 and 4, mix the first precipitate, the second precipitate, and other precipitates, wash and dry them to obtain dihydroxyethylenedioxime.

[0053] In this application, by fractionating the first mother liquor, high-purity crystals can be obtained from it, and the impurity-containing second mother liquor can be recovered, reducing product loss. Introducing a co-solvent allows the formation of micelles in the mother liquor. The hydrophobic core of these micelles can "encapsulate" or adsorb some organic impurities, isolating these impurities that might otherwise interfere with crystallization or be incorporated into the crystal lattice. This purifies the crystallization environment, regulates crystal nucleation and growth, inhibits explosive nucleation, and ultimately yields uniform, pure crystals. The strategy of recycling the mother liquor maximizes product recovery from it, improving the overall yield.

[0054] In some specific embodiments, dissolving the crude dihydroxydioxime in deionized water includes: dissolving the crude dihydroxydioxime in deionized water at a first dissolution temperature of 45℃-85℃, stirring for 5min-45min to obtain a first mother liquor.

[0055] In this embodiment, the high solubility of dihydroxyethylenedioxime in hot water is utilized to dissolve most of the product, forming a first mother liquor. It should be understood that at this point, the mass fraction of dihydroxyethylenedioxime in the first mother liquor is less than or equal to the saturation solubility of dihydroxyethylenedioxime at this first dissolution temperature, ensuring that all dihydroxyethylenedioxime in the first crude dihydroxyethylenedioxime product can be completely dissolved in deionized water.

[0056] For example, the first dissolution temperature can be a range of 45°C, 55°C, 65°C, 75°C, 85°C or any combination thereof; the stirring time can be a range of 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min or any combination thereof.

[0057] In some specific embodiments, the mass fraction of dihydroxyethyl oxime in the first mother liquor is 0.61wt%-1.80wt%, preferably 1.48wt%-1.80wt%.

[0058] In this embodiment, by controlling the mass fraction of dihydroxyethylenedioxime in the first mother liquor between 0.61 wt% and 1.80 wt%, it is possible to ensure that a sufficient amount of high-purity first precipitate is obtained when the first mother liquor is allowed to stand, while also ensuring that enough product remains in the second mother liquor as "seed" or "base material," providing the possibility for high-yield, controllable crystallization after the addition of the second crude product. More importantly, the core of crystallization is supersaturation, which is the driving force for crystal nucleation and growth. Too high a supersaturation will trigger explosive nucleation, instantly generating a large number of tiny crystal nuclei, resulting in a fine and non-uniform product. By precisely controlling the mass fraction of dihydroxyethylenedioxime in the first mother liquor, the initial supersaturation of the third mother liquor in the second step is indirectly controlled, thereby making the particle size of the second precipitate more uniform and the yield higher.

[0059] For example, the mass fraction of dihydroxyethyl oxime in the first mother liquor can be 0.61 wt%, 0.65 wt%, 0.70 wt%, 0.75 wt%, 0.80 wt%, 0.85 wt%, 0.90 wt%, 0.95 wt%, 1.00 wt%, 1.10 wt%, 1.20 wt%, 1.30 wt%, 1.40 wt%, 1.45 wt%, 1.48 wt%, 1.50 wt%, 1.60 wt%, 1.70 wt%, 1.80 wt%, or any combination thereof.

[0060] In some specific embodiments, adding a co-solvent to the second mother liquor can, on the one hand, raise the nucleation energy barrier, prevent the disordered generation of a large number of new crystal nuclei, and effectively suppress the primary nucleation of dihydroxydioxime seeds in the second mother liquor; on the other hand, it can allow crystallization to grow mainly based on the existing limited number of crystal nuclei, guiding secondary nucleation; and furthermore, it can allow solute molecules to arrange themselves in an orderly manner on a controlled number of crystal nuclei, promoting the orderly growth of crystals, thereby growing larger and more uniform crystals.

[0061] In some specific embodiments, the first mother liquor is allowed to stand and then separated and collected, including: allowing the first mother liquor to stand at a temperature of less than or equal to 30°C for 48h-96h, then filtering it to obtain the second mother liquor and the first precipitate.

[0062] It's understandable that most impurities remain relatively soluble at higher temperatures, thus retaining more in the second mother liquor. When crystallizing the first mother liquor, controlling the settling temperature to be less than or equal to 30°C minimizes impurity interference in the crystallization environment, resulting in a higher purity first precipitate. Furthermore, the nucleation and growth rate of dihydroxyethylene dioxime is relatively slow; extending the settling time to 48-96 hours allows the crystals ample time to "correct" their structure. This makes the resulting first precipitate easier to filter and wash, with less mother liquor (containing impurities) entrained. Therefore, controlling the settling temperature of the first mother liquor to be less than or equal to 30°C and setting it for 48-96 hours promotes orderly molecular arrangement, resulting in crystals with more complete crystal forms, larger particle sizes, and a denser structure.

[0063] For example, the settling temperature of the first mother liquor can be a range of 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 25°C, 28°C, 30°C, or any combination thereof. The settling time of the first mother liquor can be a range of 48h, 60h, 72h, 84h, 96h, or any combination thereof.

[0064] In some embodiments, after separating the first mother liquor, the obtained solid can be washed and dried with ethanol to obtain a first precipitate. Meanwhile, during the collection of the first precipitate, the precipitate on the container wall is rinsed with water, the rinsed water is mixed with the filtrate, and a co-solvent is added to obtain a second mother liquor.

[0065] Specifically, the solid obtained after filtration is washed 2-3 times with industrial alcohol and dried in a water bath oven at 60°C for 6 hours to obtain the first precipitate.

[0066] In some specific embodiments, the mass concentration of the co-solvent in the second mother liquor is 0.5 mg / mL to 2.0 mg / mL.

[0067] In this embodiment, by controlling the mass concentration of the co-solvent in the second mother liquor to be between 0.5 mg / mL and 2.0 mg / mL, its molecules can be fully adsorbed onto the surface of newly generated crystal nuclei, forming an adsorption film. This adsorption film forms an energy barrier, increasing the energy required to form a stable new crystal nucleus. This significantly suppresses the "explosive nucleation" phenomenon that causes a large number of crystal nuclei to form instantaneously. Because the number of crystal nuclei is effectively controlled, the supersaturated solute in the solution has more opportunities to grow orderly and uniformly on the limited number of existing crystal nuclei, thus forming larger and more uniform crystals. When the co-solvent concentration reaches or exceeds the critical micelle concentration (CMC), it forms a large number of micelles in the solution. Their hydrophobic cores can act like "miniature cages," encapsulating organic impurities in the solution. This effectively purifies the microenvironment for crystal growth, greatly reducing the chance of impurities being embedded in the crystal lattice, thereby improving the purity of the final product. Moreover, by suppressing explosive nucleation and reducing impurity embedding, larger, more complete, and easier-to-filter crystals can be formed, thereby reducing product loss in the mother liquor and during filtration, indirectly increasing the yield.

[0068] For example, the mass concentration of the co-solvent in the second mother liquor can be a range of 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.2 mg / mL, 1.4 mg / mL, 1.6 mg / mL, 1.8 mg / mL, 2.0 mg / mL, or any combination thereof.

[0069] In some specific embodiments, adding the second crude dihydroxydioxime to the second mother liquor includes: dissolving the second crude dihydroxydioxime in the third mother liquor intermediate at a second dissolution temperature of 45℃-85℃, stirring for 5min-45min to obtain the third mother liquor.

[0070] When reusing the second mother liquor, the second dissolution temperature of the crude dihydroxyethylenedioxime in the second mother liquor was controlled at 45℃-85℃ to ensure its complete and rapid dissolution. Sufficient time was given for stirring for 5-45 minutes, ensuring that all solid particles, especially smaller and less noticeable particles, were completely dissolved. At this point, dihydroxyethylenedioxime dissolved at a constant high temperature, and the entire system was in a well-defined and homogeneous thermodynamic state. When the third mother liquor was cooled from the same high temperature starting point according to a preset cooling program, the entire system synchronously and uniformly entered a supersaturated state. This uniform starting point is the foundation for achieving synchronous nucleation and uniform growth.

[0071] For example, the second dissolution temperature can be a range of 45°C, 55°C, 65°C, 75°C, 85°C or any combination thereof; the stirring time can be a range of 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min or any combination thereof.

[0072] In some specific embodiments, the third mother liquor undergoes a first crystallization treatment, including: cooling the third mother liquor at a stirring rate of 200 rpm-400 rpm and a cooling rate of 0.1℃ / min-1℃ / min, then allowing it to stand at a temperature less than or equal to 30℃ for 48 h-96 h for crystallization treatment, followed by filtration to obtain a fourth mother liquor and a second precipitate; preferably, the cooling rate is 0.2℃ / min-0.5℃ / min; preferably, the standing temperature is less than or equal to 20℃; preferably, the standing time is 60 h-84 h.

[0073] It is understood that crystallization is the process by which solute molecules diffuse from the bulk solution to the crystal surface and embed themselves in the crystal lattice. In this embodiment, by controlling the stirring rate of the third mother liquor at 200 rpm-400 rpm, the flow of the third mother liquor is accelerated, reducing the thickness of the "diffusion layer" on the crystal surface. This allows solute molecules to be transported to each crystal surface more quickly and uniformly, avoiding "agglomeration" or "clumping" and improving particle size uniformity. Moreover, at this stirring rate, local supercooling of the third mother liquor can be avoided, achieving synchronous crystallization and facilitating the acquisition of products with narrow particle size distribution. Controlling the cooling rate of the third mother liquor at 0.2℃ / min-0.5℃ / min can further control the number of nuclei, laying the foundation for particle size distribution, promoting orderly crystal growth, and improving product quality.

[0074] Decreased solubility means that a large amount of product originally dissolved in the solution will crystallize out due to supersaturation, becoming a second precipitate. The lower the crystallization endpoint temperature, the lower the concentration of residual product in the fourth mother liquor, which is equivalent to "extracting" more product from the mother liquor, thereby greatly improving the overall recovery rate of this step and even the entire process. Therefore, controlling the temperature of the third mother liquor for static crystallization to be less than or equal to 20°C can maximize the product yield without excessively increasing energy consumption, and rely on the selectivity of low-temperature crystallization itself and the synergistic effect with the co-solvent to ensure the high purity of the final product.

[0075] For example, the stirring rate can be a range of 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, or any combination thereof; the cooling rate can be a range of 0.1℃ / min, 0.2℃ / min, 0.3℃ / min, 0.4℃ / min, 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min, 1.0℃ / min, or any combination thereof. The settling temperature can be a range of 10℃, 12℃, 14℃, 16℃, 18℃, 20℃, 25℃, 28℃, 30℃, or any combination thereof; the settling time can be a range of 60h, 62h, 64h, 66h, 68h, 70h, 72h, 74h, 76h, 78h, 80h, 82h, 84h, or any combination thereof.

[0076] In some specific implementations, the number of repetitions in step four is greater than or equal to 3.

[0077] The recrystallization method provided in this application recycles the mother liquor, controls the number of cycles, reintroduces crystals that do not meet the particle size requirements into the crystallization system, and removes residual impurities from the mother liquor. The use of a co-solvent balances crystal growth and nucleation rates, reduces the formation of excessively fine particles, and improves particle size uniformity, thereby increasing the recrystallization yield and particle size uniformity of dihydroxyethylenedioxime.

[0078] This application also provides a dihydroxyethylenedioxime, the particle size of which is 800μm-2500μm; the standard deviation of the particle size of the dihydroxyethylenedioxime is less than or equal to 60μm.

[0079] Figure 1 This is a schematic diagram of the crystal structure of dihydroxyethylenedioxime obtained by the recrystallization method provided in this application. Figure 1 As can be seen, the dihydroxyethylenedioxime obtained by recrystallization in this application exists in the form of needle-like and rod-like crystals, and some are also aggregated in clusters. From Figure 1 Judging from the scale size, the crystal size of dihydroxydioxime is approximately in the range of hundreds of micrometers to millimeters.

[0080] Figure 2 PXRD spectra of dihydroxyethylenedioxime obtained by the recrystallization method provided in this application and a standard DHG sample. From Figure 2 It is evident that the dihydroxyethylenedioxime provided in this application exhibits crystal plane diffraction peaks consistent with those of the standard DHG sample, without interference from impurity peaks. This indicates that the purity of the dihydroxyethylenedioxime provided in this application is close to that of the standard DHG sample.

[0081] Figure 3 A schematic diagram showing the particle size and particle size distribution of dihydroxyethylenedioxime obtained by the recrystallization method provided in this application. From... Figure 3 As can be seen, the particle size of the obtained dihydroxyethyl oxime is mainly distributed between 2000 μm and 2500 μm, and the particle size is relatively high.

[0082] The DHG crystals prepared in this application exhibit significant advantages in particle size uniformity and purity. Their regular crystal morphology and narrow particle size distribution meet the stringent requirements of downstream applications such as energetic materials and fuel additives. High purity (≥99.5%) and low impurity content ensure their stability and safety in oxidizer or combustion improver applications. Simultaneously, the smooth, defect-free crystal surface enhances their gas source diffusion efficiency in pesticide fumigants. Furthermore, the crystals obtained through a mother liquor recycling process demonstrate excellent thermal stability, and their decomposition products are predominantly fuel-rich gases, meeting environmental and safety requirements. In summary, this product surpasses existing technologies in performance, environmental friendliness, and economic efficiency.

[0083] This application also provides an additive comprising the above-mentioned dihydroxyethylenedioxime.

[0084] In some specific implementations, the additive can be an energetic material, a fuel additive, or a pesticide fumigation additive, etc.

[0085] The additive provided in this embodiment can perform the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0086] The technical solution of this application will be further described below using specific embodiments.

[0087] Example 1

[0088] A method for recrystallizing dihydroxyethyl oxime includes the following steps:

[0089] Step 1: Weigh 4.0g of crude dihydroxyethyl oxime and dissolve it in 650mL of deionized water at 55℃ to prepare the first mother liquor (DHG mass fraction is 0.61wt%).

[0090] Step 2: Let the second mother liquor stand at room temperature for 72 hours, and then separate and collect the second mother liquor after standing. During the collection of the first precipitate, rinse the precipitate on the container wall with water. Wash the filter cake obtained after filtration with industrial alcohol 2-3 times, and dry it in a water bath oven at 60°C for 6 hours to obtain 2.47 g of dihydroxyethylenedioxime, with a yield of 61.75%. Combine the water used to rinse the container wall with the filtrate, and add 0.65 g of sodium dodecyl sulfate (SDS) to the filtrate to dissolve it, thus obtaining the second mother liquor (SDS concentration of 1.0 mg / mL).

[0091] Step 3: Add 3.50g of crude dihydroxyethyl oxime to 650ml of the second mother liquor, stir at 55℃ for 10min to obtain the third mother liquor (DHG mass fraction is 0.61wt%).

[0092] Step 4: Let the third mother liquor stand for 72 hours and filter it; during the collection of the second precipitate, rinse the precipitate on the container wall with water; wash the filter cake obtained after filtration with industrial alcohol 2-3 times and dry it in a water bath oven at 60℃ for 6 hours to obtain 3.37g of the second precipitate, with a yield of 96.29%; combine the water used to rinse the container wall with the filtrate to obtain the fourth mother liquor;

[0093] Step 5: Repeat steps 3 and 4, and recrystallize to obtain dihydroxyethyl oxime.

[0094] The quality of the crude product used in steps three, four, and five, the crystallization settling time, the yield of the precipitate, and the yield are detailed in Table 1.

[0095] Table 1

[0096]

[0097] As shown in Table 1, six mother liquor circulation experiments were conducted under the crude product dissolution condition of 55℃, and the yield of precipitate (DHG) was above 90% in each experiment.

[0098] Example 2

[0099] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 1, except that the mass of the first crude dihydroxyethylenedioxime is 7.13 g, the dissolution temperature is 65 °C, the mass fraction of dihydroxyethylenedioxime in the first mother liquor is 1.09 wt%, and the mass of the first precipitate is 5.74 g, with a yield of 80.50%. The mass of crude product used for recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 2.

[0100] Table 2

[0101]

[0102] As shown in Table 2, six mother liquor recycling experiments were conducted at 65℃ for crude product dissolution. Only the yield of the fifth recycling experiment was slightly less than 90%, while the yields of the others were all above 90%.

[0103] Example 3

[0104] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 1, except that the mass of the first crude dihydroxyethylenedioxime is 9.03 g, the dissolution temperature is 75 °C, and the volume of deionized water is 600 ml; the mass fraction of dihydroxyethylenedioxime in the first mother liquor is 1.48 wt%; the mass of the first precipitate is 7.07 g, with a yield of 78.29%; and the mass of SDS added is 0.6 g (mass concentration of 0.77 mg / mL). The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 3.

[0105] Table 3

[0106]

[0107] As shown in Table 3, six mother liquor recycling experiments were conducted at 75°C for dissolving the crude product. Only the second and sixth recycling experiments had yields less than 90%, while the yields of the rest were all above 90%. However, compared with Example 2, the yields of each recycling experiment were reduced.

[0108] Example 4

[0109] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 1, except that the mass of the first crude dihydroxyethylenedioxime is 12.01 g, the dissolution temperature is 85 °C, and the volume of deionized water is 670 ml; the mass fraction of dihydroxyethylenedioxime in the first mother liquor is 1.76 wt%; the mass of the first precipitate is 10.25 g, with a yield of 85.35%; and the mass of SDS added is 0.67 g (mass concentration of 1.0 mg / mL). The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 4.

[0110] Table 4

[0111]

[0112] As shown in Table 4, six mother liquor recycling experiments were conducted at a crude product dissolution temperature of 85°C. All mother liquor recycling experiments achieved a single-step yield of over 90%, and the yields obtained in each cycle were higher than those in Examples 1-3. This indicates that a higher recrystallization recycling yield can be obtained when the crude product is dissolved in the mother liquor at 85°C.

[0113] Example 5

[0114] A recrystallization method for dihydroxyethyl oxime is provided, which is basically the same as that in Example 4, except that the mass concentration of SDS added in the second mother liquor is 0.5 mg / ml. The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 5.

[0115] Table 5

[0116]

[0117] Example 6

[0118] A recrystallization method for dihydroxyethyl oxime is provided, which is basically the same as that in Example 4, except that the mass concentration of SDS added in the second mother liquor is 0.4 mg / ml. The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 6.

[0119] Table 6

[0120]

[0121] Example 7

[0122] A recrystallization method for dihydroxyethyl oxime is provided, which is essentially the same as that in Example 4, except that the concentration of SDS added in the second mother liquor is 2.0 mg / ml. The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 7.

[0123] Table 7

[0124]

[0125] Example 8

[0126] A recrystallization method for dihydroxyethyl oxime is provided, which is essentially the same as that in Example 4, except that the concentration of SDS added in the second mother liquor is 2.1 mg / ml. The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 8.

[0127] Table 8

[0128]

[0129] As shown in Tables 5-8, the recycling yield and particle size uniformity in Examples 5 and 7 are superior to those in Examples 6 and 8. This indicates that when the mass concentration of SDS in the second mother liquor is 0.5 mg / mL-2.0 mg / mL, a higher recrystallization yield from the mother liquor recycling and better particle size uniformity of dihydroxyethylenedioxime can be obtained.

[0130] Example 9

[0131] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 1, except that the dissolution temperature of the first crude dihydroxyethylenedioxime in deionized water is 85°C. The mass of the crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 9.

[0132] Table 9

[0133]

[0134] Example 10

[0135] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 2, except that the dissolution temperature of the first crude dihydroxyethylenedioxime in deionized water is 85°C. The mass of the crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 10.

[0136] Table 10

[0137]

[0138] Example 11

[0139] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 3, except that the dissolution temperature of the first crude dihydroxyethylenedioxime in deionized water is 85°C. The mass of the crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 11.

[0140] Table 11

[0141]

[0142] Compared with the results of Examples 1-3, Examples 9-11 showed better yields and particle size uniformity. This indicates that the higher the temperature at which the crude product is dissolved in the mother liquor, the higher the yield of dihydroxyethylenedioxime and the better the particle size uniformity.

[0143] Example 12

[0144] A recrystallization method for dihydroxyethylenedioxime is provided, which is basically the same as that in Example 4, except that the settling time for each crystallization is different and the number of cycles is 7. The mass of crude product used in the cycles, the settling time for crystallization, the yield of precipitate, and the yield are detailed in Table 12.

[0145] Table 12

[0146]

[0147] Example 13

[0148] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 4, except that during the recycling process, the third mother liquor is subjected to a stirring program for cooling, thereby achieving cooling crystallization of dihydroxyethylenedioxime. The stirring rate is 300 rpm, the cooling rate is 0.25 °C / min, the settling temperature during crystallization is 25 °C, and the settling time is 4 h. The mass of crude product used in the recycling, the settling time during crystallization, the yield of precipitate, and the yield are detailed in Table 13.

[0149] Table 13

[0150]

[0151] Compared to Example 4, the recrystallization yield and particle size uniformity of the mother liquor recycling in Example 13 were higher. This indicates that recrystallization using a gradient cooling method can yield dihydroxyethylenedioxime with higher yield and better particle size uniformity.

[0152] Example 14

[0153] A recrystallization method for dihydroxyethyl oxime is provided, which is basically the same as that in Example 13, except that the cooling rate is 0.1 °C / min during the cycle. The mass of crude product used in the cycle, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 14.

[0154] Table 14

[0155]

[0156] Example 15

[0157] A recrystallization method for dihydroxyethylenedioxime is provided, which is essentially the same as that in Example 13, except that the cooling rate during the cycle is 0.5 °C / min. The mass of crude product used in the cycle, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 15.

[0158] Table 15

[0159]

[0160] Example 16

[0161] A recrystallization method for dihydroxyethylenedioxime is provided, which is essentially the same as that in Example 13, except that the cooling rate during the cycle is 1.0 °C / min. The mass of crude product used in the cycle, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 16.

[0162] Table 16

[0163]

[0164] Example 17

[0165] A recrystallization method for dihydroxyethyl oxime is provided, which is essentially the same as that in Example 13, except that the cooling rate during the cycle is 1.1 °C / min. The mass of crude product used in the cycle, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 17.

[0166] Table 17

[0167]

[0168] Compared with Example 17, Examples 13, 15, and 16 have smaller particle size standard deviations. This indicates that when performing gradient cooling crystallization, controlling the cooling rate between 0.1℃ / min and 1℃ / min can yield dihydroxyethylenedioxime with better particle size uniformity.

[0169] Example 18

[0170] A recrystallization method for dihydroxyethylenedioxime is provided, which is basically the same as that in Example 13, except that the settling temperature during crystallization is 20°C during the cycle. The mass of crude product used in the cycle, the settling time for crystallization, the yield of precipitate, and the yield are detailed in Table 18.

[0171] Table 18

[0172]

[0173] Compared to Example 13, Example 18 yielded a higher yield. This indicates that appropriately reducing the settling time during crystallization is beneficial for obtaining a higher yield of dihydroxyethylenedioxime.

[0174] Comparative Example 1

[0175] A recrystallization method for dihydroxyethyl oxime is provided, which is essentially the same as that in Example 1, except that SDS is not used. The mass of crude product used for recycling, crystallization settling time, precipitate yield, and yield are detailed in Table 19.

[0176] Table 19

[0177]

[0178] Comparative Example 2

[0179] A recrystallization method for dihydroxyethylenedioxime is provided, the process of which is basically the same as that in Example 1, except that deionized water is used instead of the mother liquor during the recycling process. The mass of crude product used in the recycling, the crystallization settling time, the precipitate yield, and the yield are detailed in Table 20.

[0180] Table 20

[0181]

[0182] As shown in Table 1-18, the recrystallization method using mother liquor recycling provided in this application yields dihydroxydioxime in a yield of not less than 80%, and the standard deviation of the particle size of the obtained dihydroxydioxime is less than 60 μm.

[0183] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for recrystallizing dihydroxyethyl oxime, characterized in that, include: Step 1: Dissolve the crude dihydroxyethyl oxime in deionized water to obtain the first mother liquor; Step 2: Let the first mother liquor stand and perform a first separation, collect the filtrate, add a co-solvent to the filtrate, and perform a second separation to obtain a second mother liquor and a first precipitate; Step 3: Add crude dihydroxyethyl oxime to the second mother liquor to obtain the third mother liquor; Step 4: Crystallize the third mother liquor to obtain the fourth mother liquor and the second precipitate; Step 5: Repeat steps 3 and 4 to wash and dry the first precipitate, the second precipitate, and other precipitates to obtain the dihydroxyethylenedioxime; The co-solvent includes at least one of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate.

2. The recrystallization method of dihydroxyethylenedioxime according to claim 1, characterized in that, The process of dissolving the first crude dihydroxyethyl oxime in deionized water includes: The crude dihydroxyethyl oxime was dissolved in deionized water at a first dissolution temperature of 45℃-85℃ and stirred for 5min-45min to obtain the first mother liquor. And / or, the step of allowing the first mother liquor to stand and performing a first separation includes: After the first mother liquor is left to stand at a temperature of less than or equal to 30°C for 48-96 hours, the first separation is performed, and the filtrate is collected. And / or, the addition of the second crude dihydroxyethyl oxime to the second mother liquor comprises: The second crude dihydroxyethyl oxime was dissolved in the second mother liquor at a second dissolution temperature of 45℃-85℃, and stirred for 5min-45min to obtain the third mother liquor; And / or, the crystallization treatment of the third mother liquor includes: The third mother liquor is cooled at a stirring rate of 200 rpm to 400 rpm and a cooling rate of 0.1 °C / min to 1 °C / min. Then, it is allowed to stand at a temperature of less than or equal to 30 °C for 48 h to 96 h for crystallization treatment and filtration to obtain the fourth mother liquor and the second precipitate.

3. The recrystallization method of dihydroxyethylenedioxime according to claim 1, characterized in that, The first mother liquor contains dihydroxyethylenedioxime; The mass fraction of dihydroxyethyl oxime in the first mother liquor is 0.61wt%-1.80wt%.

4. The recrystallization method of dihydroxyethylenedioxime according to claim 3, characterized in that, The mass fraction of dihydroxyethyl oxime in the first mother liquor is 1.48wt%-1.80wt%.

5. The recrystallization method of dihydroxyethylenedioxime according to claim 1, characterized in that, The mass concentration of the co-solvent in the second mother liquor is 0.5 mg / mL to 2.0 mg / mL.

6. The recrystallization method of dihydroxyethylenedioxime according to claim 1, characterized in that, The third mother liquor includes dihydroxyethylenedioxime; The mass fraction of dihydroxyethylenedioxime in the third mother liquor is 0.53wt%-1.57wt%.

7. The recrystallization method of dihydroxyethylenedioxime according to claim 1, characterized in that, The mass fraction of dihydroxyethylenedioxime in the third mother liquor is 1.16wt%-1.80wt%.

8. The recrystallization method of dihydroxyethylenedioxime according to claim 2, characterized in that, During the crystallization process, the cooling rate is 0.2℃ / min-0.5℃ / min; And / or, the settling temperature is less than or equal to 20°C; And / or, the settling time is 60h-84h.

9. The recrystallization method of dihydroxyethylenedioxime according to claim 1, characterized in that, The number of repetitions in step four is greater than or equal to 3.

10. A dihydroxyethylenedioxime, characterized in that, Obtained by recrystallization method according to any one of claims 1-9.

11. The dihydroxyethylenedioxime according to claim 10, characterized in that, The particle size of the dihydroxyethylenedioxime is 800μm-2500μm; And / or, the standard deviation of the particle size of the dihydroxydioxime is less than or equal to 60 μm.

12. An additive, characterized in that, Includes dihydroxyethyl oxime as described in any one of claims 10-11.

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